This invention relates to a improved adjustable wear sensor assembly for an adjustable clutch, and more specifically, to an adjustable wear sensor assembly bushing wherein the location of a locating flange on the bushing is adjustable.
Clutches are utilized in many vehicle drive applications. As is known, a clutch selectively transmits or breaks a drive connection between an engine and a transmission. In one common type of clutch which is widely utilized in heavy vehicles, a clutch includes a pressure plate which rotates with a clutch cover. A fulcrum selectively forces the pressure plate against a member which is to be driven to rotate with the pressure plate and clutch cover. When the pressure plate is forced against the driven member, it sometimes must move to accommodate wear on friction surfaces in the clutch. This wear adjustment is widely utilized in modern heavy vehicle clutch applications.
Wear adjustment is typically achieved by using a wear sensor assembly that senses the wear within the clutch. The wear sensor assembly cooperates with an adjustment assembly that adjusts the location of the clutch components relative to one another to maintain pedal travel parameters and proper operation of the clutch. There are numerous wear sensor assemblies that have been used in the prior art.
In one very standard way of sensing wear, at least one pin, typically four, is fixed to the pressure plate. A bushing is received in the clutch cover and has a flange that abuts the clutch cover and locates the bushing and the clutch cover relative to the pressure plate. The pin is interference fit within a bushing such that movement of the bushing relative to the pin is normally restricted. Thus, the pin typically moves with the bushing, and the pressure plate is maintained at a distance from the clutch cover. However, with wear, sometimes upon application of the clutch, the pressure plate must move an additional amount relative to the clutch cover to fully engage the driven member. When this happens the pressure plate is forced further and the pin may move through its interference fit in the bushing to allow the pressure plate to fully engage the clutch.
The distance between the pressure plate and clutch cover must be set at assembly of the clutch to ensure proper wear adjustment and clutch operation. Since the flange is integral with the bushing in prior art arrangements, the distance between the pressure plate and clutch cover must be set by installing shims between the flange and clutch cover to obtain a "zero gap" in the clutch's engaged position and compensate for tolerances, which is time consuming and costly.